It has been an ongoing goal of mankind to continuously design improved system by which potential energy, in the form of a hydrocarbon-based fuelstock, may be converted into useful work. Presently, the world's automotive industries are attempting to develop more efficient combustion engines which at the same time release decreased levels of undesirable gaseous emissions during their operation. The instant invention relates to fuel compositions for use in internal combustion engines. The compositions disclosed herein are suitable for use in four cycle engines, and are especially suitable for operating two-cycle combustion engines.
By far the most common type of combustion engine presently in popular usage is the four-cycle gasoline engine. During its normal operation, four strokes or motions of the piston and connecting rod assembly in the cylinder bore comprise one complete engine cycle. These strokes are: 1) Fuel-air intake stroke, 2) compression stroke, 3) power stroke, and 4) exhaust stroke. This cycle is repeated at a constant or varied rpm in order to provide a useful work output at the crankshaft. One of the drawbacks of the four-cycle engine is that only one power stroke occurs during every two revolutions of the crankshaft to which the piston and its connecting rod are attached. Such cyclic motion causes a significant amount of friction to be generated between moving components during normal engine operation, with attendant waste of some of the fuel's energy as dissipated heat.
Two-cycle engines, on the other hand produce one power stroke for every one revolution of the crankshaft. Typical operation is as follows: On the upstroke of the piston a partial vacuum is created in the crankcase and the piston is simultaneously caused to uncover a fuel mixture inlet port forcing the fuel mixture to enter the crankcase. This occurs while the charge currently in the cylinder is being compressed. The compressed charge is then fired and the piston decends on its power stroke, compressing the mixture in the crankcase. At the bottom of the power stroke, the piston uncovers the exhaust port(s) and fuel transfer ports. The exhaust gasses exit the engine while fresh fuel mixture is admitted to the cylinder. The cycle then repeats.
For two cycle engines conventional fuel mixtures comprise gasoline and a soluble lubricating additive such as a petroleum oil in a ratio of about 16 parts gasoline to 1 part of lubricating additive. Many different lubricating additives are currently available under the generic name of "2-cycle engine oil". The 2-cycle engine oils which are available and which are well known in the prior art may contain one or more of the following additives: anti-oxidant, corrosion inhibitor, detergent, metal deactivator, anti-icing agent, intake system deposit control additive, anti-surface ignition agent, biocide, dispersant, demulsifying agent, and lubricating oil. One of the requirements of fuel compositions for two-cycle engines is that they provide for sufficient lubrication of the moving engine components so as to avoid engine seizure and undue wear while preventing build-up of carbon deposits in the combustion chamber, piston ring sticking, and problems associated with storage of the engine. Examples of prior art U.S. patents pertaining to two-cycle engine fuels include: U.S. Pat. Nos. 2,896,593; 3,004,837; and 3,753,905.
From a manufacturing standpoint, an advantage of using a conventional two-cycle fuel mixture is that no oil flow passages must be cast in or machined in the engine block and that no oil recirculation pump is required. Therefore the cost of manufacturing two cycle engines is considerably less when compared to four-cycle engines. Also, since the engine delivers one power stroke per engine revolution using fewer moving parts, efficiency of energy conversion is increased while less friction is generated. Although the total cost per gallon of the fuel employed may be increased significantly through use of the instant invention, the benefits reaped in terms of increased fuel economy and the economics of engine manufacture shall make it cost effective overall.
The major disadvantage of combusting two-cycle fuel mixtures and the main reason why these types of engines do not enjoy the same popularity as their four-stroke counterparts is that the amount of carbon monoxide, nitrogen oxides, and particularly unburned hydrocarbons emitted during their operation is too great for the current emmission standards maximum levels imposed by the US EPA and other similar organizations worldwide even when state-of-the-art catalytic convertors are utilized. Obviously, if it were possible to reduce the level of undesirable emissions while maintaining sufficient lubrication for normal engine operation, then the automotive industries and society as a whole would benefit greatly.